Ricardo seminar explores how Europe’s new signalling specifications will support cross-border rail

The Technical Specification for Interoperability - which covers control-command and signalling subsystems (CCS TSI) - was updated in 2023 to replace the previous 2016 version.

The main driver of the change is to encourage the increased use of European Rail Traffic Management System ERTMS technology on cross-border rail across the EU.

ERTMS is an interoperable signalling and speed control system that the EU's railways are required to introduce on mainline routes. As well supporting increased speed and safety levels, the adoption of a common signalling technology will also reduce procurement and maintenance costs. 

To date, however, ERTMS projects have been country-based, with its use on cross-border routes still limited. The 2023 TSI CCS – which also sets mandatory requirements for technology security – was therefore developed, in part, to address this gap in ERTMS adoption, by improving the alignment of national products and specifications.

Technical seminar hosted by Ricardo Certification

To help rail managers and safety specialists understand the update, Ricardo Certification hosted a seminar to examine the reasoning behind the change, assess the impact on cross-border rail in the short- and medium-terms, and discuss the implications for operators and manufacturers.

Jerry Borger, lead assessor at Ricardo Certification, opened the session by setting the TSI update within the wider context of the EU railway.

“Although TSI CCS includes the rules for ETCS (European Train Control System, part of ERTMS), it does not actually offer a complete set of requirements for realising a train security system. Most requirements in the update are assigned to the onboard systems on the vehicles so they can travel across national borders without interruption”. 

“For the technical implementation of the infrastructure, the TSI CCS allows more room for flexibility, in order to continue to use existing operational processes and signalling and interlocking systems in different Member States as much as possible.”

Jerry then pointed out that, where the 2016 version of the TSI CCS used three different requirements or baselines (BL2, BL3MR1 and BL3R2), the new version has only one: baseline 4 (BL4). 

“Note that within this one BL4 distinction are four different so-called System Versions (2.1, 2.2, 2.3 and 3.0),” he continued. “The complexity of the parallel use of these versions will continue as the GSM-R radio system - which is used within ETCS to transmit the status of the signals, among other things - will be replaced by FRMCS (Future Railway Mobile Communication System) in the coming years.”

“To determine the exact functionality of an ETCS infrastructure or train system, it is necessary to not only know the System Version, but also which error corrections, or Change Requests (CR), have been implemented”, he explained. 

"The now considerable list of CRs is centrally maintained by the ERA (European Railway Agency). All in all, that means there is a large number of theoretical combinations, from ETCS variations in the infrastructure to ETCS variations in the train.”

“According to current insights, only some of these combinations in practice lead to a security system in which the system works well together on the train and in the infrastructure,” said Jerry. “With infrastructure steadily changing, it is therefore not only a big puzzle for carriers to determine where, when and which equipment can be driven under ETCS, but it also requires a lot of effort to have the necessary on-board adjustments carried out in time.”

The application of the new TSI CCS has been mandatory since its introduction in August 2023. “But as long as the underlying requirements (called Subsets) have not yet been fully published, the current ETCS built-in or conversion projects often use the transitional arrangement, which allows the substantive requirements from previous TSI CCS to be followed”.

Jerry concluded that “The ongoing development of the specifications of the ETCS system, defined by constantly new CRs and system versions, means that its goal of making cross-border train traffic simpler and more efficient still lies some way into the future. Also, the systems already installed in the train, and in the infrastructure, will have to be regularly adapted to the new specifications.”

Editor's note: During the ERTMS Congress of ERA in Valenciennes, several stakeholders called for a pause on the release of new TSIs and underlying specifications for the time being, allowing EU member states to focus on the rollout of ERTMS.